This invention pertains to mooring ropes and cables and more particularly it pertains to an anchor rode having an extensible segment built therein and a method for manufacturing this extensible segment.
Stretchable cordage are used as mooring cables and anchor rodes for partly absorbing the stresses caused by wave actions on small boats, on buoys or on similar floating structures, for preventing damage to these crafts and floating structures and for preventing the loosening of their anchors. Stretchable cordage are also used as tow ropes for dampening the shocks of pulling an object from rest. Some of the stretchable cordage of the prior art are described in the following documents:
U.S. Pat. No. 4,258,608 issued on Mar. 31, 1981 to John L. Brown;
U.S. Pat. No. 4,426,908 issued on Jan. 24, 1984 to Martin Ullmann;
U.S. Pat. No. 4,534,262 issued on Aug. 13, 1985 to Richard C. Swenson;
U.S. Pat. No. 4,597,351 issued on Jul. 1, 1986 to Edward C. Brainard, II;
U.S. Pat. No. 5,483,911 issued on Jan. 16, 1996 to Ronald N. Kubli, and
CA 1,087,930 issued on Oct. 21, 1980 to Bertil Brandt.
Generally, the stretchable ropes of the prior art are made of a rubber rod or tube enclosed in the central portion of a rope. A tension on the rope causes the braided outside layer of the rope to compress the rubber core radially, which causes the rope to elongate, thus providing the rope with elastic properties. The length and diameter of the rubber core is proportional to these elastic properties.
An anchor rode is often partially wound on a capstan or around sheaves, and has shackles or knots at both ends thereof. Therefore, an anchor rode needs to be non-elastic along the segments thereof which are used for tying and along the segments susceptible to slippage and sharp bending. Hence, it is often desirable to make only a short segment of the anchor rode extensible as opposed to its full length.
In the past, this characteristic has raised difficulties in preventing the longitudinal movements of rubber core inside the base rope during repeated elongations and retractions of the rope. The methods of the prior art to retain the rubber core inside the base rope consists of using high strength tape and ring clips to squeeze the base rope at each end of the rubber core. It is believed that theses tapes and clips are subject to deterioration from fatigue stress and exposure to the harsh environment in which these ropes are used. Consequently, the ropes must be inspected often and repaired in order to maintain their integrity.
Moreover, the rubber cores in the stretchable ropes of the prior art are generally not subject to elongation with the outside layer of the base rope. The relative movement of the outside braided layer over the rubber core during repeated elongations and retractions causes friction and wear of the outside braided layer and of the rubber core. It will be appreciated that all relative movements between the outside braided layer and the rubber core have an adverse effect on the useful life of the rope.
Although the elastic cordage of the prior art deserve undeniable merits, it is believed that a need still exists for an extensible segment in an anchor rode, in which the rubber core does not move inside the braided outside layer of the base rope and consequently reduces the friction wear inside the base rope in order to prolong the useful life of the anchor rode.
In the present invention, there is provided an extensible segment in an anchor rode in which the rubber core is held longitudinally along the central axis of the base rope, to reduce friction related wear of the base rope and of the rubber core.
Broadly, the extensible segment in an anchor rode comprises a rubber core enclosed in a braided base rope along the central axis of the base rope. A braided cover further encloses an intermediate portion of the rubber core inside the base rope. The braided cover is made of braided cover strands embedded in the rubber core, and un-braided cover strands extending over the two ends of the rubber core. The un-braided cover strands are weaved into the base rope to retain the rubber core longitudinally inside the base rope.
The extensible segment according to the present invention is advantageous to disperse peak load in an anchor rode. Its construction prevents the rubber core to move along the base rope during repeated elongation and retractions of the rope, and enhances the resiliency of the extensible segment by applying tension as well as compression stresses to the rubber core. Friction generated by relative movement between the rubber core and the base rope is practically eliminated due the encapsulated braided cover being in contact with the braids of base rope.
Still another feature of the present invention is that it is susceptible of a low cost of manufacture with regard to both materials and labour, and which accordingly is then susceptible of low prices of sale to the consumer, thereby making such extensible segment economically available to the public.
Other advantages and novel features of the present invention will become apparent from the following detailed description.